Increased emission standards have lead fuel injector manufacturers to operate at higher injection pressures. For example, typical common rail injectors are now injecting fuel at pressures between 250 and 300 MPa. In order to reach these higher injection pressures, control valves within fuel injectors must operate with precision in an environment free from fuel debris and contaminants. Thus, it is increasingly important fuel to be filtered before being delivered to control valves.
Control valves within injectors perform a myriad of tasks related to injection. In order to repeatedly perform these tasks, control valves are assembled to exacting standards. These standards make control valves susceptible to and more affected by damage from debris that may be contained within the fuel supplied thereto. It has been recognized that debris from fuel damages control valves much more than any other valves (e.g., check valves) within the injector. Damaged control valves ultimately lead to injector failure.
Previous attempts to filter fuel within an injector have always been in “series.” In other words, said attempts have stubbornly sought to filter all fuel delivered to the injector and ultimately both the control and check valves. This has typically been done by inserting a filter at or near the high-pressure fuel inlet of the injector. Inserting filter at this point ultimately fails and allows debris into the injector for at least two reasons. First, by attempting to filter all high-pressure fuel provided to the injector, the limits of the filter efficiency dictate that at least a small percentage of debris will ultimately get through the filter and potentially have access to the control valve. Secondly, when a filter in series becomes inundated with debris such that the filter can catch no more debris, a pressure drop across the filter occurs. The increasing pressure behind the filter eventually overcomes the blockages and pushes debris through the filter; into the injector; and ultimately to the sensitive control valve.
By counter-intuitively realizing that not all valves need the same level of protection by the filter, the present disclosure seeks primarily to protect the sensitive control valve. It does this by filtering the fuel within the injector in “parallel” as opposed to in “series.” In other words, fuel delivered to the control valve is filtered while the fuel provided to the check valve may or may not be filtered. The filter in the present disclosure is positioned adjacent the control valve and downstream of the fuel supply inlet. In so doing, the disclosed fuel injector is directed to overcoming one or more of the problems set forth above.